pin fdm_materials to 5.5.0

Contributes to CURA-11218

conanfile.py

@@ -319,7 +319,7 @@ class CuraConan(ConanFile):
             self.requires("cura_private_data/(latest)@ultimaker/testing")
             self.requires("fdm_materials/(latest)@internal/testing")
         else:
-            self.requires("fdm_materials/(latest)@ultimaker/stable")
+            self.requires("fdm_materials/5.5.0")
 
     def build_requirements(self):
         if self.options.devtools: